I will use the iPad for lots of big games like N.O.V.A and large gameloft games that take up about 300mb each. Lots of those and some productivity apps.
I will also use the ipad for a couple of ebooks. How much does each use in space. I will also have a couple of full length movies that take up like 1GB each.
Maybe a few photo albums with 20+ photos in each
And internet browsing.